Webster Build

[simister]

Thanks Gail,

 

[Brian Rupnow]

Congratulations John--I knew you'd get there.---Brian

 

[10K Pete]

Very nice!! That's a great runner, and I love the sound of the exhaust. Is the 'muffler' the one on the drawings?

Pete

 

[canadianhorsepower]

Very nice job Thm:Thm:

love the spark plug CAP Rof}Rof}Rof}

 

[simister]

Thanks guys.

Yes, Pete, it is the same muffler as the drawings.

 

[bmac2]

Congratulations John th_wav
You’ve got a good runner there. That’s actually pretty go throttle response for a Webster. I’ve been following along from the start and it’s sure nice to see. I wish I’d thought of that spark plug cap . . . wouldn’t have tasered myself so many times trying to adjust the carb.

 

[simister]

HI Bob,

I still managed to taser myself with the plug. I have now fitted a proper insulated plug.

John

 

[Longboy]

Yes! Good job John on troubleshooting the start up issues. We'll have Brian send you a check for a job well done! On one of the second hand carburetors on an engine I used had the same loose throttle problem. I used a light smear of 5 minute epoxy mixed about 1: 1/2 and put it on the barrel and turned back and forth as it dried to a soft sticky. Enough to open and close by hand but engine vibs don't move it any more.Thm: Dave

 

[simister]

Thanks Dave, today I made a throttle handle with a friction screw joined to the carby, and it works quite well. I got the idea from one of Brian's posts where he did a similar thing. The epoxy idea also sounds like a good solution.

John

 

[gus]

Hi John,

A MasterPiece by a MasterCraftsMan. I am very impressed with the hand start. Your Webster beat mine hands down.

 

[simister]

Thanks Gus, There are plenty of imperfections when you look closer. I am just happy that it runs.

I will post a photo of the throttle mod later today.

John

 

[simister]

This is the modification that I did as a throttle friction control. I got the idea from Brian's post. Works well Brian,

John

 

[Brian Rupnow]

AhHa--the old "Casey Jones throttle trick"!!! It does work well. I was afraid to try the two part epoxy trick on my carburetor, as I was afraid it might glue everything up solid. I never thought to mention the con-rod hitting the side of the cylinder where is exits through the bottom of the cylinder as a possible source of "engine knock", although it has happened to me too. In my case it was easily solved by rounding the edges of a rectangular or square con rod to give that tiny bit of clearance needed. That is a tricky one, because when modeling it in 3D cad, if you take a cross section view on the center of the con rod it will show a clearance. It doesn't take into account that the cylinder curves upward on each side of the centerline and fouls the lower corners of the rod. ---Brian

 

[pkastagehand]

. That is a tricky one, because when modeling it in 3D cad, if you take a cross section view on the center of the con rod it will show a clearance. It doesn't take into account that the cylinder curves upward on each side of the centerline and fouls the lower corners of the rod. ---Brian

Should be able to move the section view off center to near edge of con rod? Seems like most CADs will let you take a section wherever you want? (Not that I have a ton of 3D CAD experience and none at all with Solidworks; if that's what you're using.)

Paul

 

[Brian Rupnow]

Should be able to move the section view off center to near edge of con rod? Seems like most CADs will let you take a section wherever you want? (Not that I have a ton of 3D CAD experience and none at all with Solidworks; if that's what you're using.)

Paul

Yes, I could do that---If I had thought of it---

 

[pkastagehand]

Yes, I could do that---If I had thought of it---

Yes, of course; Hindsight is an exact science.

 

[simister]

" the old Casey Jones throttle". I used to watch that series when I was a kid.

How long can the Webster run before overheating?

What are the symptoms and end result from running the Webster too long, apart from it getting very hot?

After I have run it for a short time it seems to get very hot. Being only air cooled it must have some limitation.

John

 

[Brian Rupnow]

If it gets too hot, it will gradually slow down and stop because of increased binding between the cylinder and the piston. If you are running cast iron rings, it may or may not "unseize" when it cools off. If you are running a Viton o-ring on the piston, then overheating is not a good thing, because apparently Viton releases some really horrible acid when it overheats and melts. I have been repeatedly warned by various doom criers that if any of my engines get THAT hot, that the melted o-ring acid will eat off my fingertips "right down to the bone!!!"---I'm not sure that I believe them, but I try and run some kind of cooling fan on my engines now.----OR---maybe nothing will happen. A lot depends on the clearances in the engine, the speed it is ran at, and the ability of the fins to radiate heat away as it builds up. The longest I have ever ran my Webster is about half an hour.

 

[Cogsy]

I have been repeatedly warned by various doom criers that if any of my engines get THAT hot, that the melted o-ring acid will eat off my fingertips "right down to the bone!!!"---I'm not sure that I believe them

Viton o-rings are rated for applications around 400F and there would be a significant safety factor as well, so the chances of one melting or catching fire in a small engine would be very slim I imagine.

However, when they do melt or catch fire they decompose into hydrogen fluoride. On contact with moisture or skin this becomes hydrofluoric acid - which boils at room temperature, dissolves corneas! and burns really badly. Check the picture of burnt fingers at the bottom of this link.

So it looks like everyone is right, they do work in engines and they will cause you severe injuries if they fail catastrophically.

 

[Longboy]

Its unlikely that one would have any overheating on an air cooled model engine like Webster or others of similar types that are demonstrated in a fast idle condition even during one after another tankful runs. I have been all around my engines with an infrared thermo gun and at the cylinder head spark plug area the temps are hottest at around 270 Degs in a Tucson July day inside the garage. No issues but it gets hot enough to where WD40 smoke rises out of the exhaust valve guides. Enough radiator draws the heat from the cyl. heads and I am ready to call it a day after a tank or two in summertime here!

On those fractional displacement model airplane engines running 5 figure RPM's, they generate lots of heat. Overheating is abated not through radiator size per se, but massive airflow across the finning by prop wash.

As has happened to me, lack of proper lubrication in the fuel mix would be the #1 reason for hot engine stall and since the model is not usually under a heavy throttle load will just stop running without any damage to metal or plumbing o-rings.